Companies and organizations often have business processes that are performed on a routine basis. The processes can involve multiple discrete or composite actions, some of which can be performed in any order, others which must be performed in parallel or in some other specific order. Such processes are often modeled as workflows. A workflow can be the orchestration of multiple actions. Computer systems can be used to process workflows and orchestrate the execution of the component actions. In order to facilitate processing of a workflow by a computer system, the workflow can be defined in a workflow definition language (WDL). Graphical tools have been created to simplify the process of defining workflows in various WDLs.